Under present technical conditions, an Organic Light Emitting Diode (OLED) display device has spatial and temporal non-uniformity, and as a size of the display device increases, such problems become more and more apparent, so how to solve the non-uniformity of display of the large-sized OLED display device becomes one of key technologies. The non-uniformity of display of the OLED display device is closely related with the manufacturing process; when threshold voltages of pixels of an entire display panel are quite different, overall luminance uniformity of the display device will be deteriorated. Moreover, organic material is accompanied with the problem of luminance changing in its service life. Hence, various compensation methods are needed to improve the non-uniformity of display.
The compensation method may be divided into two categories: internal compensation and external compensation. The internal compensation refers to a method for compensating using a sub-circuit constructed by a Thin Film Transistor (TFT) inside a pixel; the external compensation refers to a compensating method in which a TFT or OLED signal is extracted out of the display panel, and then by using an outside Application Specific Integrated Circuit (ASIC) outside, the compensating is performed. Generally, both the pixel structure and driving mode of the internal compensation are relatively complex; and in display applications of large size, high resolution and high refresh rate, the internal compensation method may cause a decreased aperture ratio and a slow driving speed; while the external compensation has a simple pixel structure, a faster driving speed and a better compensation effect.
The external compensation may be further divided into an optical extraction mode and an electrical extraction mode depending on different data extraction methods. The optical extraction mode refers to extracting a luminance signal by an image sensor, for example, photographing of a Charge Coupled Device (CCD), after the display panel is lightened; and the electrical extraction mode refers to extracting an electrical signal of the TFT and the OLED by a sensing circuit of a driving chip. Since the signals extracted by the two methods are different in type, data processing methods are also different. However, a highly efficient luminance compensation method is needed at present.